Remotely actuated vacuum coaxial switch with reduced-in-thickness contact portions for eliminating cross-talk



Feb. 23, 1965 T. N. TILMAN 3,171,090 REMOTELY ACTUATED VACUUM COAXIAL swn'ca WITH REDUCED-IN-THICKNESS CONTACT PORTIONS FOR ELIMINATING CROSS-TALK Original Filed Nov. 10. 1959 INVENTOR. 720 IV. 774 MAN United States Patent 3,171,096 REMUTELY ACTUATED VAQUUM CGAXIAL SWITCH WITH REDUCED IN Ti-HCKNESS CONTACT PfiRTiONS FOR ELIMHQATRNG QRGSS-TALK Ted N. Tillman, San .iose, Qalifi, assignor, by mesne assignments, to Jennings Radio Manufacturing Corporation, San dose, Qaiiih, a corporation of Delaware Continuation of application Ser. No. 852,165, Nov. 19, 1959. This application May 4, 1954, Ser. No. 365,$6tl 14 Qlaims. (Cl. 333-4) My invention relates to coaxial switches, and more particularly to a vacuum coaxial switch which may be actuated from a point remote from its installation. This application is a continuation of my copending application Serial No. 852,105, filed November 10, 1959, now abandoned.

One of the principal objects of the invention is the provision of a vacuum coaxial switch capable of manual, electromechanical or pneumatic operation according to the requirements of the user.

Another object of the invention is the provision of a vacuum coaxial switch suitable for use in aircraft and missiles where low weight and independence from en vironmental characteristics such as rapid pressure and temperature changes are of major importance.

Still another object of the invention is the provision of a vacuum coaxial switch in which the impedance is maintained constant throughout the switch, and in which the impedance may be varied or matched with existing transmission lines merely by changing the proportions of the switch.

A still further object of the invention is the provision of a coaxial switch suitable for use with pressurized transmission lines, thus permitting a high dielectric strength to be maintained in the entire transmission system.

A further object of the invention is the provision of a vacuum coaxial switch in which the movable contact is of a low inertia type, thus making possible extremely high speed operation of the switch over extended periods.

Another object of the invention is the provision of a vacuum coaxial switch in which the contact mechanism is grounded when the switch contacts are opened in order to reduce the coupling capacity between the terminal ends of the transmission lines and the hot common contact, thus reducing the cross-talk between these elements in the open circuit condition of the switch.

Another object of the invention is the provision of a vacuum coaxial switch which allows at least up to a 50 kw. transmission line to switch hot with little or no danger of destroying the switch.

Still another object of the invention is the provision of a vacuum coaxial switch which will permit switching of one transmitter between two antennas or one antenna between two transmitters, or which can be combined in multiple units into a network that will handle any practicable number of antennas and transmitters.

The invention possesses other objects some of which with the foregoing will be brought out in the following description of the invention. I do not limit myself to the showing made by the said description and the drawings, since I may adopt variant forms of the invention within the scope of the appended claims.

Referring to the drawings:

The figure is a vertical half-sectional view, with parts of the device shown in elevation. The view is drawn approximately full size.

Broadly considered, the vacuum coaxial switch of my invention comprises a hermetically sealed and evacuated metallic housing having a main portion and a transversely extending portion. Extending hermetically into each of the main and transverse portions of the housing is an Buli'lfilhh Patented Feb. 23, 1965 'ice inner conductor coaxially arranged within and insulated from its associated housing portion. Each of the inner conductors terminates within the housing in a fixed contact point spaced from the adjacent fixed contact points, and means are provided to rigidly support the inner contact point ends of the inner conductors in fixed and vibration-free position. Preferably, the inner conductor extending into the transverse housing portion constitutes a common conductor supplying high radio frequency power from an appropriate source. Mounted on the housing and movable into and out of engagement with an associated pair of said spaced fixed contact points within the housing to make or break circuit therethrough, is a mobile contact means responsive to control from a point remote to the installation of the switch. Means are provided for detachably coupling the outer ends of the outer terminals and said inner conductors with associated transmission lines.

There is a continuing need in the radio and television industry for switch gear which provides vacuum coaxial switching for high power transmitters, high power antennas, dummy loads or any combination of these. Some of the characteristics desirable in such switch gear includes ease of operation either manually, electromechanically or pneumatically, preferably from a station remote from the installation of the switch. The switch should be such that it is capable of miniaturization to make it suitable for different environments such as aircraft and missiles, and it should be constructed so as to have a minimum of cross talk, and to need little or no maintenance after installation. Preferabl the switch should have a low VSWR and be capable of rapid sequential switching, and of switching a hot 50 kw. transmission line. By rapid operation is meant operation from open to closed position, or from closed to open position in a matter of only a few milliseconds.

To provide these desirable characteristics and others which will become apparent from the description which follows is the primary purpose of the present invention. To achieve this end, I provide an outer unitary metallic T shaped hollow housing, having a main portion 2 corresponding to the bar of a T, and a transverse portion 3 corresponding to the stem thereof. The outer remote open ends of the main housing portion constitute integral aligned conductive outer terminals 4 and 6, adapted to be detachably connected to associated coaxial transmission lines, while the remote open end of the transverse portion constitutes a conductive outer terminal 7 integral with but transversely disposed to the axially aligned terminals 4 and 6. To hermetically seal the housing, each of the integral terminal ends is sealed adjacent its open outer end by an annular metallic apron or expansion ring 8 having one edge portion or end 9 integrally and hermetically high temperature brazed about the metallized outer periphery 12 of an annular dielectric wall 13, and its other expanded end 14 integrally and hermetically brazed to the inside surface 16 of the associated outer terminal portion of the housing.

Sealing the opening in each of the annular dielectric walls is an inner metallic conductor coaxially arranged with respect to the associated outer terminal portion. The inner conductors extend through the central openings of the annular walls, and in the main housing portion they are axially aligned, with corresponding ends spaced apart and extending in opposite directions. Each of the inner conductors coaxially arranged within the aligned outer terminals of the main housing portion comprises an out- .ardly opening hollow cylindrical cup-shaped terminal portion having side walls 17 and a bottom 18. Integrally brazed to the bottom 18, and extending into the housing in a direction opposite to the side walls 17, is a cylindrical intermediate conductive portion 19 having an integral radially extending peripheral flange 21 cooperating with the portion 1? to provide a seat in which is hermetically high temperature brazed the radially inturned flange 22 of an expansion sleeve 23, the other end of which is brazed hermetically within the metallized inner periphery 24 of the associated dielectric wall. It will thus be seen that the inner and outer conductors cooperate with the dielectric walls and the hermetically intervening sleeves or expansion rings to hermetically seal the housing to provide an enclosed chamber 26 therein capable of being evacuated to a remarkably high degree. Evacuation is effected through tubulation 27, the outer end of which (not shown) is pinched off and sealed when the desired degree of evacuation has been reached.

Within the evacuated chamber, each of the aligned and spaced coaxially arranged inner conductors terminates in a conically tapered portion having on its apex end a rigid fixed contact point 28. A dielectric post 29, having its opposite ends metallized, is integrally interposed between each contact point 28 and the associated outer housing, and functions to absorb lateral stresses imposed on the contact point and therefore the inner conductor when the switch is operated to close a circuit therethrough.

The inner conductor coaxially arranged within the transverse housing portion also comprises a hollow cylindrical cup-shaped terminal portion having side walls 17 and a bottom 18. Integrally brazed to the bottom 13 on the side opposite the walls 17 is a hollow intermediate conductive portion 31 having a radially extending flange 32 thereon intermediate its ends, an inner end portion 33 of the intermediate hollow conductor 31 being increased in diameter. A fixed contact point 34, integrally brazed to the inner end of the hollow intermediate conductor provides a contact surface 36 lying in a horizontal plane with a contact surface 38 on the adjacent fixed contact 28. It will thus be seen from the drawing that the fixed contact point 34 on the transverse inner conductor lies intermediate and spaced from the contacts 28, which are equally spaced on opposite sides of the central contact 34. To insure that this relationship is maintained, a dielectric post 37 having one end embedded in the contact point 34, extends axially therefrom and is integrally caught at its other end in a metal plug 39 integrally and hermetically united with the main housing portion 2. The dielectric post, rigidly interposed as it is between the contact 34 and the outer wall, serves to insulate the contact from the housing, and also absorbs any lateral and axial stresses which may be imposed on the contact 34 and its associated inner conductor. As with the axially aligned inner conductors 19, an expansion sleeve 23 having an inturned flange 22 brazed hermetically to the radial flange 32 is interposed between the dielectric wall 13 and the inner conductor to seal the aperture therethrough.

It is of paramount importance in high power coaxial switches that there be a minimum of capacitance between the contact points. Capacitance between the contacts when the switch is in open circuit position results in the transfer of energy between the open contacts, an undesirable condition known in the trade as cross talk. It has been found through experiments that maintaining as large a gap as possible, with a minimum of opposed contact surfaces, results in the virtual elimination of capacitance and therefore of cross talk at the rated capacity of the switch. For this reason, in the present device, the contact points 28 are reduced in thickness to present only a thin edge to the adjacent contact 34, which in turn is provided with a radially extending flange 41 of approximately the same thickness, formed by an abrupt reduction in the diameter of the contact 34. The thin edges of contact 28 and flange 41 thus present a minimum amount of opposed area between which capacitance may exist, while the associated surrounding structure recedes away from these edges so as to increase the distance and still further minimize the possibility of capacitance between adjacent conductors.

Integrally brazed on each of the outer terminal end portions 4, 6 and '7 of the housing 2-3 is a swivel connector ring 42 having a radially outwardly extending flange 45 and a radially inwardly extending flange 44 abutting the outer end of the associated terminal. The radially outwardly extending flange 43 cooperates with the ring body to provide a shoulder against which flange 4-6 on swivel connector 47 may abut. The swivel connector 47 is provided with apertures 48 through which connection can be made with a complementary associated flange (not shown) on a coaxial transmission line. A cylindrical flange 49 on the ring 42 cooperates with the radially inwardly extending flange 44 to provide a seat within which an outer peripheral edge of a dielectric annulus 51 may lie. As shown in the drawing, the flange 49 and the swivel connector 47 are proportioned to provide a recess 52 within which a gasket may be inserted when the switch is detachably connected to a pressurized transmission line. The entire transmission line may then be pressurized in order to increase the dielectric strength of the atmosphere between inner and outer conductors. Apertures 53 in each of the dielectric walls 51 insures that the T-shaped housing not included in the vacuumized chamber is also pressurized with the transmission line.

(looperating with the swivel flange assembly which detachably connects the outer housing to the outer conductors of an associated transmission line system, is a detachable resilient coupling 54 having a reduced diameter portion 56 at one end adapted to fit snugly within the inner periphery of the associated dielectric annulus 51. At its other end the coupling is provided with resilient fingers 57 adapted to be inserted and resiliently retained within the open end of the inner conductor of an associated coaxial transmission line. To secure the coupling 54 to the annulus 51, and also to provide a means for detachably connecting the coupling to the hollow terminal end of the inner conductor, a head 53 having a threaded shank 59 and a peripheral groove 6?. is provided. The shank detachably engages a complementarily threaded bore in the coupling, thus binding the wall between the coupling and the head 58. The partsare proportioned so that a fiat spring 62 lying in the groove 61 exerts a resilient pressure against the inner surface of the cylindrical walls 17 of the associated inner conductor. There is thus established a secure and rigid, yet detachable, mechanical and electrical connection between the inner conductors of the switch and the inner conductors of associated coaxial transmission lines.

In the embodiment of my invention shown in the drawing, each of the inner conductor assemblies coaxially arranged within the main and transverse outer housing portions are adapted to be fabricated as a separate unit, and as a unit inserted into position and fixed in place. To accomplish this, the transverse and main outer terminal portions 7, 4- and 6 are each constructed in two axially arranged parts, with their adjacent ends formed to provide an overlapping slide joint as at 63. Integrally interposed between the overlapping ends of the two parts are a pair of rings 64 and 66, having cylindrical flanges 67 and 68, respectively, proportioned so that flange 67 nests within flange 63. The edges of the flanges are then heliarc brazed as at 69 in order to hermetically seal the joint. It will thus be apparent that the interior of the hollow housing with the terminal assemblies removed may effectively be cleaned to eliminate contaminants, and that subsequently the previously cleaned transverse and main inner conductor assemblies may be inserted and fixed in place without further contamination of the interior of the envelope. This insures a long trouble-free life for the switch components sealed within the evacuated housing.

Movably mounted on the conductive outer housing 2 is a mobile contact assembly operable from outside the housing to make or break a circuit through adjacent inner conductors of the switch. In the embodiment of the switch shown, the transverse conductor constitutes a come mon conductor, utilized to selectively connect either or both of the adjacent axially aligned inner conductors with a common source of power. As shown, a mobile contact assembly is associated with each of the aligned inner conductor contact points 28. In the drawing, the left hand mobile contact assembly has been shown in a closed circuit position, while the right hand mobile contact assembly has been shown in an open circuit position. It will be apparent from the drawing that each mobile contact assembly may be operated individually, or that the two may be ganged for simultaneous operation, and that any suitable actuator mechanism may be utilized.

Each mobile contact assembly comprises a cylindrical metallic shell or tube 71 extending into the evacuated chamber in a direction parallel to the axis of the transverse housing portion. The tube is integrally and hermetically brazed intermediate its ends to the housing wall, and Within the housing terminates in a free end 72 spaced above contact surface 38 of contact 28 and contact surface 36 of contact flange 41. Experiment has shown that this spacing of the tube above the contact surfaces is important in determining the impedance through the switch.

On its outer end, the cylindrical tube '71 is provided with an integral cap 73 having a radially extending mounting flange 74 to which may be attached any desirable means for actuating the mobile contact assembly, such as a solenoid (not shown). The cap is also provided with a cylindrical flange 76, within which the outer open end 78 of a flexible metallic bellows 79 is hermetically and integrally heliarc brazed at 80. A bearing tube 81 heliarc brazed within the open end of the bellows and extending thereinto provides a slide bearing for a conductive metallic actuator stem 82 having threads 83 on its outer end for connection to the actuating means.

Bellows and stem extend coaxially inwardly into the tube toward the fixed contact points 28 and 34, each terminating intermediate the ends of the tube. A coupling block 84 brazed on the inner end of the actuator stem provides a radially extending flange 86 on which the inner periphery of an annular metallic plate 87 is hermetically brazed. The outer peripheral portion of the plate 37 is hermetically brazed to the inner end of the bellows so that bellows and actuator stem are integrally and hermetically united. A dielectric pillar or post 88 having one end embedded and brazed in the lower end of the coupling block 84, extends axially downwardly and terminates in the central bore of a metallic contact support block 89 brazed on the end of the post 88. The contact support block 89 is provided with a pair of axially spaced radially extending flanges 91 and 92 adjacent its lower end defining between them a groove 93 within which a contact blade 94 and a reenforcing contact cone 96 are confined. For assembly purposes the lower flange 92 may be formed by a ring slipped over the end of the support block and heliarc brazed in position after the contact blade and cone are placed on the support block. It will of course be obvious that if the blade has a circular configuration the necessity of aligning the blade w1th the longitudinal axis of the main housing portions is eliminated.

Each of the contact blades 94 is provided with a head 97. which, in the position of the parts illustrated in the left hand assembly, forms a line contact with the adjacent flat contacting surfaces 36 and 38. In the position of the parts illustrated in the right hand assembly the contact blade has been pulled up into engagement with the lower end of the tube 71. The contact blade and the structure associated with it is therefore grounded to the housing when a selected switch assembly is operated to open the circuit. This has the effect of placing the grounded contact assembly closer to either of the associated contacts 28 or 34 than these contacts are to each other, thus insuring that if a transfer of energy occurs, it will occur between the grounded contact assembly and 6 an associated contact point and not between the spaced and disconnected contact points.

From the foregoing it will be seen that the present invention provides a coaxial switch which is both light and rigid, capable of being exhausted to provide a contaminant free atmosphere for longer switch life, and capable of being interposed quickly and easily in an established transmission line, even of the pressurized type. It will also be apparent that the bellows assembly does not carry any radio frequency energy whatsoever, and that the light weight of the contact blade, having a low inertia factor, permits extremely rapid operation of the switch, in the order of only a few milliseconds to open or close the switch, for many thousands of operations per hour over an extended period.

I claim as my invention:

1. A coaxial switch for coaxial transmission line circuits comprising a metallic housing having a main portion and a transverse portion, a dielectric wail hermetically and movably connected for expansion across each portionof the housing and forming and enclosing therewith a vacuumized chamber, a first conductor coaxial with the main housing portion and extending hermetically through its respective wall into said chamber, said first conductor having a flat and reduced in thickness contact portion extending axially into said chamber with the adjacent portion of the conductor increasing in size and tapering as it recedes from the contact portion, a second conductor coaxial with the transverse housing portion and extending hermetically through its respective wall into said chamber, said second conductor having a relatively thin contact portion projecting therefrom and spaced from and oppositely disposed to said flat contact portion on the first conductor whereby the conductive capacity between the oppositely disposed contact portions is minimized, and mobile contact means having hermetic sealing means connecting it to the housing for operative movement to connect or disconnect said contact portions on the first and second conductors within said vacuumized chamber to make or break a circuit through the switch.

2. A coaxial switch for coaxial transmission line circuits comprising metallic housing having a main portion and a transverse portion, a dielectric wall hermetically connected for expansion across each portion of the hous' ing and forming and enclosing therewith a vacuumized chamber, a first conductor coaxial with the main housing portion and extending hermetically through its respective wall into said chamber, said first conductor having a contact portion of relatively thin cross section extending axially into said chamber with the adjacent portion of the conductor increasing in cross section as it recedes from the contact portion, a second conductor coaxial with the transverse housing portion and extending hermetically through its respective wall into said chamber, said second conductor having a relatively thin contact portion projecting therefrom and spaced from and oppositely disposed to said relatively thin contact portion on the first conductor whereby the conductive capacity between the oppositely disposed contact portions is minimized, mobile contact means mounted on the housing for operative movement to connect or disconnect said contact portions on the first and second conductors within said vacuumized chamber to make or break a circuit through the switch, said mobile contact means being of relatively light weight conductive material and when moved having a low inertia whereby the mpedance is maintained constant throughout the switch and said contacts being of low inertia type permit extremely high speed operation over extended periods.

3. The combination according to claim 2, in which detachable lead means are provided for detachably coupling the conductors into a circuit, said detachable lead means having a housing means detachably connected to said main housing and a dielectric Wall supporting coaxially a detachable coaxial member to its respective conductor.

4. The combination according to claim 2, in which means are provided to electrically ground said mobile contact means when it is moved to disconnect said first and second conductors.

5. The combination according to claim 2, in which said mobile contact means includes a stem movably mounted on the housing and extending into said chamber and having hermetic means connecting it to the housing, and a conductive contact blade fixed on the stern within the chamber and movable by said stern into and out of engagement with said conductors.

6. The combination according to claim 2, in which said mobile contact means includes a slide bearing fixed on the housing, a stem slidably supported in the bearing and extending into the chamber, a bellows integrally interposed hermetically between the bearing and the stem, and a conductive contact blade fixed on the stern within the chamber and movable by said stem into and out of engagement with said conductors.

7. A coaxial switch for coaxial transmission line circuits comprising a metallic housing having a main portion and a transverse portion, a dielectric wall hermetically and expansibly mounted for expansion across each portion of the housing and forming and enclosing therewith a vacuumized chamber, a first conductor coaxial with the main housing portion and extending hermetically through its respective wall into said chamber, said first conductor having a flat and reduced in thickness contact portion extending axially into said chamber, a second conductor coaxial with the transverse housing portion and extending hermetically through its respective wall into said chamber, said second conductor having a relatively thin contact portion projecting therefrom and spaced from and oppositely disposed to said flat contact portion on the first conductor whereby the conductive capacity between the oppositely disposed contact portions is minimized, and mobile contact means having hermetic sealing means connecting it to the housing for operative movement to connect or disconnect said first and second conductors within said vacuumized chamber to make or break a circuit through the switch, whereby the impedance is maintained constant throughout the switch and said contacts are of low inertia type permitting extremely high speed operaton over extended periods, and detachable lead means for detachably coupling the conductors into a circuit, said detachable lead means having a housing means detachably connected to said main housing and a dielectric wall supporting coaxially a detachable coaxial member to its respective conductor, said detachable lead means having at opposite ends thereof resilient means for detachably engaging an associated conductor and transmission line.

8. A coaxial switch for coaxial transmission line circuits comprising a metallic housing having a main portion and a transverse portion, a dielectric wall hermetically and cxpansibly mounted for expansion across each portion of the housing and forming and enclosing therewith a vacuumized chamber, a first conductor coaxial with the main housing portion and extending hermetically through its respective wall into said chamber, said first conductor having a fiat and reduced in thickness contact portion extending axially into said chamber, a second conductor coaxial with the transverse housing portion and extending hermetically through its respective wall into said chamber, said second conductor having a relatively thin contact portion projecting therefrom and spaced from and opposite ly disposed to sai fiat contact portion on the first conductor whereby the conductive capacity between the oppositely disposed contact portions is minimized, and mobile contact means having hermetic sealing means connecting it to the housing for operative movement to connect or disconnect said first and second conductors within said vacuumized chamber to make or break a circuit through the switch, whereby the impedance is maintained constant throughout the switch and said contacts are of low inertia type permitting extremely high speed operation over extended periods, means to electrically ground said mobile contact means when it is moved to disconnect said first and second conductors, said means to electrically ground the mobile contact means comprises a conductive shell integral with the housing and extending into the chamber to terminate in spaced relation to said first and second conductors and selectively engageable by the mobile contact.

9. A coaxial switch for coaxial transmission line circuits comprising a metallic housing having a main portion and a transverse portion, a dielectric wall hermetically and expansibly mounted for expansion across each portion of the housing and forming and enclosing therewith a vacuumized chamber, a first conductor coaxial with the main housing portion and extending hermetically through its respective wall into said chamber, said first conductor having a flat and reduced in thickness contact portion extending axially into said chamber, a second conductor coaxial with the transverse housing portion and extending hermetically through its respective wall into said chamber, said second conductor having a relatively thin contact portion projecting therefrom and spaced from and oppositely disposed to said flat contact portion on the first conductor whereby the conductive capacity between the oppositely disposed contact portions is minimized, and mobile contact means having hermetic sealing means connecting it to the housing for operative movement to connect or disconnect said first and second conductors within said vacuumized chamber to make or break a circuit through the switch, whereby the impedance is maintained constant throughout the switch and said contacts are of low inertia type permitting extremely high speed operation over extended periods, said mobile contact means includes a stem movably mounted on the housing and extending into said chamber and having hermetic means connecting it to the housing, a conductive Contact blade fixed on the stem within the chamber and movable by said stem into and out of engagement with said conductors, said stem including a dielectric portion and a conductive portion conductively related to the metallic housing, and wherein said conductive blade is fixed on the dielectric portion and electrically insulated from the conductive portion.

10. In a coaxial switch for coaxial transmission line circuits, a plurality of metallic outer terminal portions mounted on a metaliic main housing defining a vacuum chamber, a dielectric wall hermetically connected for expansion across an end portion of each outer terminal portion and forming a wall communicating with the vacuum chamber, a first conductor coaxial with said main housing portion and extending hermetically through one of said dielectric walls into said vacuum chamber, said conductor having a contact portion of relatively thin cross section extending axially into said chamber with the adjacent portion of the conductor increasing in cross section as it recedes from the contact portion, a second conductor extending hermetically through another of said dielectric walls into the vacuum chamber in spaced relation to said contact portion on said first conductor, said second conductor having a contact portion of relatively thin cross section whereby the conductive capacity be tween the oppositely disposed contact portions is minimized, and mobile contact means mounted on said metallic main housing for operative movement to connect or disconnect said contact portions of the conductors within said vacuum chamber to make or break a circuit, said mobile contact means being of relatively light weight conductive material and when moved having a low inertia whereby the impedance is maintained constant through the switch and said contact means being of low inertia type permits extremely high speed operation over extended periods.

11. The combination according to claim 10 in which said outer terminal portions have detachable lead means provided for detachably coupling the conductors in a circuit, said detachable lead means having a housing means detachably connected to said main housing and a dielectric wall supporting coaxially a detachable coaxial member to its respective conductor.

12. The combination according to claim 10 in which means are provided to electrically ground said mobile contact means when it is moved to disconnect said first and second conductors.

13. The combination according to claim 10 in Which said mobile contact means includes a stem movably mounted on the housing and extending into said chamber and having hermetic means connecting it to the housing, and a conductive contact blade fixed on the stem within the chamber and movable by said stem into and out of engagement With said conductors.

14. The combination according to claim 10 in which said mobile contact means includes a slide bearing fixed on the housing, a stem slidably supported in the housing and extending with the chamber, a bellows integrally interposed hermetically between the bearing and the stem, and a conductive contact blade fixed on the stem within the chamber and movable by said stem into and out of engagement with said conductors.

No references cited. 

1. A COAXIAL SWITCH FOR COAXIAL TRANSMISSION LINE CIRCUITS COMPRISING A METALLIC HOUSING HAVING A MAIN PORTION AND A TRANSVERSE PORTION, A DIELECTRIC WALL HERMETICALLY AND MOVABLY CONNECTED FOR EXPANSION ACROSS EACH PORTION OF THE HOUSING AND FORMING AND ENCLOSING THEREWITH A VACUUMIZED CHAMBER, A FIRST CONDUCTOR COAXIAL WTIH THE MAIN HOUSING PORTION AND EXTENDING HERMETICALLY THROUGH ITS RESPECTIVE WALL INTO SAID CHAMBER, SAID FIRST CONDUCTOR HAVING A FLAT AND REDUCED IN THICKNESS CONTACT PORTION EXTENDING AXIALLY INTO SAID CHAMBER WITH THE ADJACENT PORTION OF THE CONDUCTOR INCREASING IN SIZE AND TAPERING AS IT RECEDES FROM THE CONTACT PORTION, A SECOND CONDUCTOR COAXIAL WITH THE TRANSVERSE HOUSING PORTION AND EXTENDING HERMETICALLY THROUGH ITS RESPECTIVE WALL INTO SAID CHAMBER, SAID SECOND CONDUCTOR HAVING A RELATIVELY THIN CONTACT PORTION PROJECTING THEREFROM AND SPACED FROM AND OPPOSITELY DISPOSED TO SAID FLAT CONTACT PORTION ON THE FIRST CONDUCTOR WHEREBY THE CONDUCTIVE 